In the past, various clamping arrangements have been proposed for clamping or supporting work pieces. A commonly used clamping arrangement is the vice which consists of two plates which are drawn together by a lead screw. While the vice is effective for holding a single work piece, or for holding parallel work pieces, it is not versatile in that the device cannot adequately cater for irregular shaped work pieces.
U.S. Pat. No. 4,767,110 (Yang) discloses a modified vice arrangement to cater for irregular shaped work pieces. Yang discloses a work table incorporating first and second vice jaws, each of which incorporate a series of connection holes. At least three clamping claws are removably mounted to the connection holes of the vice jaws, and are arranged such that one of the claws is located in one of the jaws where the other two claws are located in the other jaw. The claws are mounted to the connection holes via shanks and these shanks are eccentrically located on the claws. In this way, the respective claws can be independently moved out of respective connection holes and inserted in a different connection hole to provide longitudinal adjustability of the claws independent of the vice jaws. The claws are further arranged to rotate about their respective shanks to provide individual angular adjustability.
With the arrangement as disclosed in Yang, a work piece is clamped by firstly locating the claws in appropriate connection holes such that they are as close to the work piece as possible. The vice jaws are then brought together and at least some of the claws are rotated until such time that all the individual claws apply a force and clamp the work piece. To assist in rotation of the claws, each claw is provided with a push handle.
While the Yang patent does enable greater flexibility of the type of work pieces which can be clamped, it does have the limitation that it is required to be located on a work bench and furthermore rapid adjustment of the claws is not possible. Furthermore, the actual clamping of the work piece is difficult in that it is necessary to bring the vice jaws together, while simultaneously applying pressure on each push handle to apply a force normal to the contact surface to ensure that the claws grip the work piece properly. This applied normal force is required if there is not sufficient frictional force between the work piece and the claws to prevent the work piece from merely sliding between the two clamping claws, rather than gripping the work piece and rotating to effect clamping.